The invention concerns a method for producing a surface with predetermined roughness, in particular an e.g. cylindrical surface, that has a surface structure of predetermined geometry suitable for application of material by thermal spraying, in which a substrate surface, preferably premachined to size, a geometrically determined groove structure of minimal depth and width is introduced by means of a tool that is preferably embodied as a follow-on tool, in that a groove cross-section is processed successively to a finished size.
Moreover, the invention concerns a tool for performing such a method as well as a device for performing the manufacturing method. Components of this invention are thus moreover a suitable combination tool, including a honing tool, a manipulation device designed for handling it, as well as a mechanical processing method for a targeted and reproducible manufacture of a defined surface quality and surface geometry.
For solving certain technical problems, in particular tribological problems, it is often desired to coat surfaces of a support material with a material that has defined properties that are matched to the respective conditions of use. In comparison to solutions in which several components are joined either mechanically or by adhesive connections or brazing connection, such coatings have the advantage of an extremely compact construction combined with a relatively large contact surface of the adjoining materials so that such a joining technique is expedient in particular for thermally highly loaded components. By means of the coating an excellent material bonding results so that thermal energy can be dissipated particularly well.
In the field of metallic materials such coatings are often applied by so-called “thermal spraying” wherein, in addition to the so-called flame spraying, recently often the so-called plasma spraying process or arc spraying process has been used. In this connection, powder particles and/or wire particles are thrown or sprayed at high thermal and kinetic energy onto the surface of the substrate to be coated and form thereon, after temperature dissipation, the desired coating.
In addition to precisely maintaining process parameters for avoiding so-called coating porosities, i.e., incorporation of cavities that can no longer be filled or so-called “overspray” where a portion of the molten particles will not adhere to the substrate but will rebound, a decisive factor for a reliable utilization of this manufacturing process is the mechanical interlocking between coating and substrate in order to achieve a satisfactory high level of adhesion of the coating. In such a case there is the need to configure the substrate surface with a surface structure of predetermined geometry so that the layer will mechanically interlock uniformly across the entire surface to be coated. In this connection, it has been found that frequently it is not sufficient to roughen the substrate surface, for example, by sandblasting or waterjet blasting and/or to activate it.
When, for example, an engine block is provided with suitable coatings that are applied by thermal spraying, a wear-resistant and friction-reduced bearing surface is provided.
The applied matrix, for example, steel matrix, is subjected when in use to a significant mechanical loading so that for providing a satisfactory service life it is important to bond the coating strongly to the substrate, for example, in the form of cast aluminum. It is particularly important to process the surface of the material to be coated in such a way that a surface with precisely defined geometric parameters is produced that is particularly suitable for thermal spraying, wherein it must be ensured that the manufacturing process is designed such that the desired surface structure can be produced in a reproducible way with minimal variance in order to ensure satisfactory bonding.
In this connection, it has been considered to process by cutting the substrate surface, for example, of a cast aluminum part, by means of a follow-on tool in that a groove cross-section is successively machined to the final size with cutting teeth that engage sequentially. With currently embodied tools of this type it has been attempted to introduce structures into the premachined cylindrical surface, for example, of cast aluminum. However, in practice this proved to be problematic in that these structures cannot be introduced with constant quality and shaping into the substrate. The adhesion of the coating applied subsequently by thermal spraying varied within too wide a range. Up to now, it has therefore not been possible to employee this method for mass production.